OS : Ubuntu 18.04
現在、ソフトウェアRAIDのmdadmを使って2TBのSSD2台でRAID1を組んでいる。
ここにSSDを1台追加し、RAID5に変換してみる。
まずは状態の確認。
$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 20 12:48:38 2019
Raid Level : raid1
Array Size : 1953381376 (1862.89 GiB 2000.26 GB)
Used Dev Size : 1953381376 (1862.89 GiB 2000.26 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Fri Jan 24 09:23:16 2020
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Consistency Policy : bitmap
Name : hoge:0
UUID : e8d83f0f:f1411b0f:424916f5:4e7e31c6
Events : 11779
Number Major Minor RaidDevice State
2 8 17 0 active sync /dev/sdb1
1 8 1 1 active sync /dev/sda1/dev/sdaと/dev/sdbの2台でRAID1が組まれているのがわかる。
ここからRAID5に変更するには、–addで新しいディスクを追加し、–growでRAID5に更新すればいい。
$ sudo mdadm --add /dev/md0 /dev/sdd
mdadm: added /dev/sdd
$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 20 12:48:38 2019
Raid Level : raid1
Array Size : 1953381376 (1862.89 GiB 2000.26 GB)
Used Dev Size : 1953381376 (1862.89 GiB 2000.26 GB)
Raid Devices : 2
Total Devices : 3
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Jan 27 14:49:39 2020
State : clean
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
Consistency Policy : bitmap
Name : hoge:0
UUID : e8d83f0f:f1411b0f:424916f5:4e7e31c6
Events : 11780
Number Major Minor RaidDevice State
2 8 17 0 active sync /dev/sdb1
1 8 1 1 active sync /dev/sda1
3 8 48 - spare /dev/sdd新たに追加した/dev/sddがspareとして認識された。
$ sudo mdadm --grow /dev/md0 --level=raid5 --raid-devices=3
mdadm: level of /dev/md0 changed to raid5
$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 20 12:48:38 2019
Raid Level : raid5
Array Size : 1953381376 (1862.89 GiB 2000.26 GB)
Used Dev Size : 1953381376 (1862.89 GiB 2000.26 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Jan 27 14:51:09 2020
State : clean, reshaping
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Consistency Policy : bitmap
Reshape Status : 0% complete
Delta Devices : 1, (2->3)
Name : hoge:0
UUID : e8d83f0f:f1411b0f:424916f5:4e7e31c6
Events : 11799
Number Major Minor RaidDevice State
2 8 17 0 active sync /dev/sdb1
1 8 1 1 active sync /dev/sda1
3 8 48 2 active sync /dev/sddRaid Levelがraid5、Raid DevicesとTotal Devicesが3になった。
RAID5にしたことで、ディスクの変換が行われる。
$ cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdd[3] sdb1[2] sda1[1]
1953381376 blocks super 1.2 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
[>....................] reshape = 0.0% (685760/1953381376) finish=284.7min speed=114293K/sec
bitmap: 0/15 pages [0KB], 65536KB chunk2TBのSSDを1台追加し、RAID1からRAID5にすると約284分（4.7時間）かかる様子。
reshapeが終わったら状態を再確認。
sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 20 12:48:38 2019
Raid Level : raid5
Array Size : 3906762752 (3725.78 GiB 4000.53 GB)
Used Dev Size : 1953381376 (1862.89 GiB 2000.26 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Jan 27 18:35:18 2020
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Consistency Policy : bitmap
Name : hoge:0
UUID : e8d83f0f:f1411b0f:424916f5:4e7e31c6
Events : 13128
Number Major Minor RaidDevice State
2 8 17 0 active sync /dev/sdb1
1 8 1 1 active sync /dev/sda1
3 8 48 2 active sync /dev/sddStateがcleanで、Array Sizeも4TBになっており、無事に処理が終わった様子。
Remark for Raid5/6: You will realize that (checking with ‘df’) the size of your array has not changed. If you added one 1TB drive to your existing 3-1TB-drive-array mdadm will not automatically add the new 1TB of space. Mdadm will just spread the old 3TB-array over 4 drives occupying 750GB of each drive and leaving 250GB on each drive blank. To change that, have your array unmounted and:
resize2fs
https://raid.wiki.kernel.org/index.php/Growing
RAID5にディスクを追加しても自動で容量は増えない仕様らしい。
もし上記の手順でArray Sizeが増えていなければ、書いてあるコマンドを叩くといいはず。
試しにやってみた。
$ sudo resize2fs /dev/md0
resize2fs 1.44.1 (24-Mar-2018)
Please run 'e2fsck -f /dev/md0' first.ファイルシステムのチェックを先にしろ、と怒られた。
$ sudo e2fsck -f /dev/md0
e2fsck 1.44.1 (24-Mar-2018)
Pass 1: Checking iノードs, blocks, and sizes
Pass 2: Checking ディレクトリ structure
Pass 3: Checking ディレクトリ connectivity
Pass 4: Checking reference counts
Pass 5: Checking グループ summary information
/dev/md0: 1456414/122093568 files (0.4% non-contiguous), 415885034/488345344 blocksもう一度、
$ sudo resize2fs /dev/md0
resize2fs 1.44.1 (24-Mar-2018)
Resizing the filesystem on /dev/md0 to 976690688 (4k) blocks.
The filesystem on /dev/md0 is now 976690688 (4k) blocks long.最終チェック
$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Tue Aug 20 12:48:38 2019
Raid Level : raid5
Array Size : 3906762752 (3725.78 GiB 4000.53 GB)
Used Dev Size : 1953381376 (1862.89 GiB 2000.26 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon Jan 27 19:01:55 2020
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Consistency Policy : bitmap
Name : hoge:0
UUID : e8d83f0f:f1411b0f:424916f5:4e7e31c6
Events : 13128
Number Major Minor RaidDevice State
2 8 17 0 active sync /dev/sdb1
1 8 1 1 active sync /dev/sda1
3 8 48 2 active sync /dev/sdd無事に2TBのSSD3台で、4TBのRAID5を組むことができた。
参考
Growing - Linux Raid Wiki
raid.wiki.kernel.org
RAID-1 to RAID-5 using mdadm
As per subject. When converting from RAID-1 to RAID-5 using mdadm, why must a RAID 1 array contain 2 devices and not mor...
serverfault.com
Converting RAID1 array to RAID5 using the mdadm grow command
I have finally decided to upgrade the storage in the home theatre PC, by adding a third 3TB hard drive. The storage was ...
stevesubuntutweaks.blogspot.com
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